A Novel Thermal Insulation System for Bonded Subsea Single Pipe Wet Insulation Applications

Transcription

1 A Novel Thermal Insulation System for Bonded Subsea Single Pipe Wet Insulation Applications 18 th BHR Conference on Pipeline Protection, Antwerp, Belgium, 4 th to 6 th November 2009 Jackson, A i. Jackson, P ii. Wan, E ii. and Hegdal J.P iii ABSTRACT Insulating pipes and subsea structures is essential to avoid the possibility of wax and hydrate formation. The materials used for insulation have been around for a few decades and include polypropylenes, polyurethanes, epoxies and rubbers. As in many areas of commercial activity over this period, there have been considerable developments with regards to these materials, which have enhanced and improved their performance. More recently there have been market requirements for the development of low thermal conductivity yet high compressive strength insulation solutions. This paper will present details on a new family of subsea insulation materials with unique properties which offer alternatives to the traditional polypropylenes and polyurethanes solutions and yet cater for high temperature, unlimited water depth applications. INTRODUCTION Bonded single pipe subsea thermal insulation has been established as a reliable tool for passive flow assurance since the 1980s iv. Recent developments v have added an active component to the design of subsea pipeline and tie-back systems through inductive and conductive power input. This type of system is referred to as thermally managed. The development of materials has generally focused on four material groups; rubbers, epoxies, polyurethanes and polypropylenes, with the introduction into the market being in that chronological order. Variants of these materials; solids, foams and syntactics have provided a range of candidate materials with differing properties for use in the manufacture of commercial insulation systems to meet a wide range of operational requirements (see Table 1). Although these materials are established in the market they do not by any means represent an exhaustive list of potential materials that can be used in thermal insulation applications. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 1 of 14

2 Material K-value (W/m.K) Max. temp. ( o C) Max depth (m) Rubber (Neoprene / HNBR) / 140 Unlimited Filled (Neoprene / HNBR) / 140 Unlimited Syntactic epoxies Polyurethane wet /115 dry Unlimited Syntatcic polyurethane* wet /115 dry 300 Syntatcic polyurethane** wet /115 dry 2800 Polypropylene Unlimited Polypropylene foams m*** Syntactic polypropylene** m Table 1: Typical parameters for subsea thermal insulation materials * polymeric microspheres ** glass microspheres ***specific formulations The majority of thermally insulated subsea lines are either in-field lines, gathering lines or tie-backs. Over the past years the trend has been toward extending the usable range of tie-backs in order to maximise the number of potential satellite fields that can be successfully tied back to a given host, or to encompass sufficient reserves for a reservoir cluster to be viable. At the same time the thermal performance requirements have become ever more demanding. The need for maintaining the flow of well fluid within a given steady state window for optimal processing and minimum operational risk has led to requirements for low U-values for insulation systems. Risks associated with inhibition of hydrates and waxes over many kilometers has led to extended cool down requirements to enable decisions to be made and corrective actions to be taken in the case of a production shut-in. The advent of extended tie-backs has enabled cost effective capacity augmentation for many existing production assets; some of them nearing the end of their otherwise useful life. In addition the development of processing hubs has become increasingly popular, particularly in so called green field areas where other infrastructure is limited or non-existent, allowing for rational exploitation of oil and gas reserves which would otherwise be economically non-feasible. TRADITIONAL MATERIALS The most commonly used materials in subsea thermal insulation are polyurethanes and polypropylenes; due to their suitability for large scale production, availability of raw materials and system cost. The need for vulcanization in autoclaves has generally limited the use of rubber based systems to manifolds, jumpers and bends, whilst the need for pre-casting of shapes and long cure times have limited the use of syntactic epoxies in general to strap-on modules and single components. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 2 of 14

3 Since the mid 1990s the average length of tie-backs has steadily increased, and line burial vi and electrically heated systems have become more common vii to further stretch the limits for single pipe systems. In these cases the main workhorse has been polypropylenes as heightened complexity in the use of polyurethanes and epoxies, brought about by water absorption and property change, has led to condensation polymers being used less widely. Other than using lower density foams and syntactic materials the material choices have changed little. Recent work performed in Bredero Shaw s laboratories and plants have demonstrated the ability of styrenic alloys and blends to provide highly robust thermal insulation systems through extrusion and injection moulding. NEW FAMILY OF MATERIALS The newly developed Thermotite ULTRA family of products utilises foamed, flexibilised and solid styrenic based thermoplastic materials to provide highly robust, lay friendly and highly efficient bonded subsea thermal insulation systems capable of low U-value and great ocean depth. This paper will present the qualification and verification work performed in advance of the release of these products to the market. Styrenic materials have been established in commercial markets since the 1930s, when BASF developed the first process to isolate the resin. The material was also released into the US market in 1937 by Dow Chemical. Polystyrene was the first stable engineering polymer, having a high modulus, high dimensional stability and low distortion. Styrofoam was released onto the commercial market by Dow Chemical in At that time this was however a brittle material and needed to be further developed. Since this cautious beginning, advances in the development of the technology have made the material highly impact resistant by the addition of butadiene to the polymerisate, alternatively compounding with ABS, or increasing rigidity through the incorporation of, for example, SMA. The result is a wide range of material property envelopes from stretchy rubbers to bearing grade materials. In all cases this is a non-biodegradable material which, as it does not contain cleavable groups, is not affected by water exposure. Styrenics are also widely miscible or compatible with many high quality engineering thermoplastics, giving great flexibility in mechanical and thermal design of systems. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 3 of 14

4 Styrenic materials in general and in the case of the Thermotite ULTRA family styrenic blends and alloys, are materials that can be processed at high output rates using current extrusion and injection moulding processes. This is a significant operational advantage since these are the two most common methods of manufacture of subsea thermal insulation. These materials are also readily foamed, providing low creep foams with low k-value and low water take-up. Styrenic materials have inherently low thermal conductivity even as solids, favourable modulus values compared to polypropylenes in general, and have good low temperature properties with a Tg below -30 o C. SYSTEM BUILD The Thermotite ULTRA line pipe coating system comprises a styrenic 3-layer structure including fusion bonded epoxy, a specially designed adhesive using a blend of materials and finally a styrenic based top-coat. The insulation system is then extruded onto this base structure in the normal manner, either as solid, foam or combination of the two to the required thickness. Finally the wear coat is applied by wrap extrusion or co-extrusion to build the final system. The Thermotite ULTRA field joint system is applied according to standard practices for injection moulded polypropylene (IMPP) field joints; using modified pre-treatment values and a specific high ductility styrenic infill material. In the event of repairs, a highly robust thermoplastic repair material has been developed and extensively tested. Visually the system looks identical to any polypropylene based thermal insulation system. Bredero Shaw s development philosophy is to build on existing skill sets and adapt existing practices to bring forth a new and exciting range of thermal insulation products with a minimum of risk. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 4 of 14

5 SYSTEM BENEFITS The Thermotite ULTRA system is conveniently mobilised in existing 3-layer factories with some minor equipment and process modifications. The manufacturing process does not require twin screw or compounding extruders to blend in glass microspheres to achieve low thermal conductivity. Even as a solid, the natural thermal conductivity of the resin as a solid is lower than that of syntactic PP. At the same time however if a twin screw extruder is available at the plant of choice, it can be used for the application of the solid. This manufacturing flexibility means that Thermotite ULTRA will be available in plants worldwide using existing production practices. Thermotite ULTRA s naturally low k-value leads to a thinner insulation layer than is generally the case for polypropylene or polyurethane based systems. The ability to foam the system results in low k- values that are not readily achievable for subsea foams that must also withstand high hydrostatic pressure. This higher density system combined with its lower thermal conductivity extends cool down performance, assists in optimizing hydrodynamic response in risers and improves sea bed stability in flowlines. The insulation can store more energy with less heat loss to maintain fluid temperatures for longer periods of time. (refer to Table 3 for relative thermal diffusivity). The Thermotite ULTRA system does not contain glass microspheres, since these are not required to give high thermal performance. As a result the solid systems have unrivaled deep water performance with unlimited capability. The excellent low temperature performance of the styrenic material systems used in the Thermotite ULTRA family give benefits for cold climate reeling, while the matched flexibility of the field joint provides mechanically continuous systems with little stiffness mismatch. The low water absorption of the system and lack of cleavable groups in the resin make this materials family ideally suited to subsea operation as an exposed system, buried system and potentially as a highly performing insulant in DEH systems. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 5 of 14

6 TESTING PERFORMED The Thermotite ULTRA system has been tested extensively in the lab, on pilot scale production lines and with coated pipe produced during 5 full scale trials in three different production facilities around the world. In total, in excess of 120 pipes have been processed and tested and over 80 field joints have been applied. The results of the rigorous performance tests are presented below. Materials testing: Mechanical Mechanical testing was performed on all components of the Thermotite ULTRA system in accordance with ASTM D638 at 50 mm/min. These materials are formulated for good low temperature ductility and impact performance. As can be seen in Table 3, the ductility of the components does not show the degree of change seen with polypropylene materials, remaining high down to -10 C. This is particularly important with a view to reeling activities in cold climates, where temperatures as low as -5 C are not uncommon when pipe is collected from the spool base. Temperature ( o C) Property Unit Material Solid insulation yield % break % yield MPa break MPa Foamed insulation yield % break % yield MPa break MPa Field Joint Material yield % break % yield MPa break MPa Outer shield yield % break % yield MPa break MPa Repair material yield % break % yield MPa break MPa Table 2: Mechanical properties for ULTRA component materials Jackson et. Al. BHR Conference, Antwerp, 2009 Page 6 of 14

7 Thermal The following thermal properties have been measured on material taken from pipe (Table 3). 50 mm discs were used for thermal conductivity measurements, using PMMA as the calibration standard. Specific heat capacity was measured using DSC at a heat rate of 10 o C/min. on 20 mg samples. As can be seen the values are generally low relative to corresponding polypropylene foams with similar modulus. Density (kg/m 3 ) K-value (W/m.K) Specific Heat (J/kg.K) Relative Diffusivity* Material 30 o C 60 o C 30 o C 60 o C 30 o C Solid Insulation Foamed 18% foaming Foamed 23% foaming Field Joint Infill Material Outer Shield Repair Material Reference high mod. PP * Normalised on PP Table 3: Thermal properties for ULTRA component materials Testing of the corrosion protection system The 3-layer corrosion protection system comprises a standard FBE coating, onto which the specially formulated ULTRABond adhesive is applied. A thicker layer of ULTRA solid is then applied onto the ULTRABond surface in the same way that the familiar 3-layer PE and PP products are produced. The resulting structure has been tested in accordance with those standards applicable for 3-Layer PP and PE with respect to CD and hot water soak. CD testing CD testing was performed at 65 o C for 48 hours at a test voltage of -1.5V and at 23 C for 28 days. The results are shown below pictorially. The system showed an average disbondment of FBE to steel of 2 mm during this test for 48 hours and 3.8 mm after 28 days. No signs of disruption of the FBE- Jackson et. Al. BHR Conference, Antwerp, 2009 Page 7 of 14

8 ULTRABond adhesion were seen. The FBE used in this trial was Scotchkote 226N from 3M, applied at a thickness of 300 microns, and the ULTRABond system was applied at a thickness of 300 microns. Figure 1: Sample after CD testing at 654oC, 48 hours, -1.5V Hot water soak testing Hot water soak testing was performed at 80 o C for 7 days. No delamination or detachment from the steel substrate was seen during the test. The FBE used in this trial was Scotchkote 226N from 3M, applied at a thickness of 300 microns, and the ULTRABond system was applied at a thickness of 300 microns. Figure 2: Sample after hot water soak testing. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 8 of 14

9 Systems testing The ULTRA product has been subjected to extensive system testing in order to demonstrate and to document the performance envelope of the product. All generally accepted installation and operation tests are complete from the point of view of the product release, however project specific requirements and product improvements will undoubtedly require re-visiting these tests from time to time. Trawl board impact testing The complete system, both solid foamed and field joint was subjected to trawl board impact testing using a pendulum impinger at an energy of 12.7 kj in accordance with the DnV trawl gear interference code DNV-RP-F111 Interference Between Trawl Gear and Pipelines. A 50 mm diameter hemispherical impinger head was used and four impingements were made, of which two coincided. Testing was performed at 4 o C. Subsequent sectioning was performed in order to determine the nature and extent of potential damage and delamination. The results of this testing are shown graphically in Figure 3. No signs of damage were seen in any of the samples, and no delamination was seen either within the insulation system or to steel. Figure 3a - c: Trawl board impact testing on (a) field joint (b) line pipe and (c) cross section after impact. Resonant fatigue testing Resonant fatigue testing has been performed at TWI on a 6 m long section of OD pipe coated with 50 mm of Thermotite ULTRA including a field joint (300 mm cutback, 8 mm overbuild, 50 mm overlap). The test, carried out for 500,000 cycles at 0.2% strain was conducted at a frequency of 20 Hz. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 9 of 14

10 The temperature of the system rose by 2 3 o C, however the test was completed without evidence of damage or deterioration. Figure 4: Fatigue test set-up at TWI. Stinger roller testing In order to address the effect of roller contact (in the case of roller boxing stinger loads) a section of pipe was subjected to a stinger roller test during which a section of pipe including a field joint was pulled beneath a 350 mm dia. roller, onto which a load of 4 tons was applied. The pull speed was ca. 2 m/min. The roller passed over the coating and field joint without sign of indentation or cracking. Subsequent dissection of the sample showed no signs of distress and no indication of delamination. Figure 5: Stinger roller test. Jackson et. Al. BHR Conference, Antwerp, 2009 Page 10 of 14

11 Tensioner clamp The ULTRA 95 system was subjected to increasing squeeze loads between two parallel thrust surfaces, mounted in an instrumented hydraulic press. Squeeze loads of up to 500 kn were applied to a 300 mm long section. The length of the touch-down onto the anvils was measured and plotted against the load applied. The sample was also inspected for any internal cracking or delamination during the test. The test set-up is shown in Figure 6. No indications of crack initiation or delamination of the sample were seen. Figure 6: Clamp arrangement for compression testing Simulated service Samples of solid and foamed systems have been subjected to simulated service testing in order to verify the k-value and creep model for system design. A sample of the solid system was subjected to simulated service testing at a variety of temperatures over a period of 49 days and at a variety of hydrostatic loadings. The sample, 50 mm of system applied to a x 15.9 mm X65 steel pipe, was instrumented with LVDT probes to record thickness change, in addition to six heat flux cells with integrated thermocouples. The results are shown below (Table 4). Jackson et. Al. BHR Conference, Antwerp, 2009 Page 11 of 14

12 Pressure Operating Duration Compressive System k-value Temperature ( o C) (Days) Creep (%) (W/mK) 50 bar bar bar bar bar bar Table 4: Results of SSV testing on the solid system As can be seen, the compressive response of the system having gained equilibrium was very small and well within the expectations for existing materials when used under similar conditions. Full scale bend test The Thermotite ULTRA system has been extensively tested for reel deployment; eight 12.2 m long x 14.3 mm pipes with 50 mm of insulation systems have been reel tested at 4 o C on a 7.5m bend former. This applies for solid, foamed and flexibilised systems. No signs of distress within or in the vicinity of the field joint were observed during the test, including no signs of localized or general overstressing. The field joint was in each case subsequently dissected and it was determined that no internal delamination or damage had been induced during the test. Figure 7: ULTRA system at full bend (outer fibre strain 2.4%). Jackson et. Al. BHR Conference, Antwerp, 2009 Page 12 of 14

13 Axial shear testing Axial shear testing has been performed on all major interfaces within the ULTRA systems at relevant temperatures reflecting operation. The values returned show a high level of cohesion between successive application steps, and also within the material itself. This is of course important for system integrity during lay and operation of the line. Testing of the innermost interface at 95 o C shows the robustness of the system at higher temperature Shear strength (Mpa) FBE - ULTRAbond (23C) 14 FBE - ULTRAbond (95 o C) 7 3-Layer - Insulation 12 Insulation - Insulation 12 Within insulation 15 Insulation - outer shield 12 Table 5: Axial shear results for ULTRA DESIGN EXAMPLES The following design examples illustrate the advantages of the ULTRA system for a range of applications relative to market incumbents: Designs are based on a x 14.3 mm steel pipe, requiring a U-value of 3 W/m 2 K on the OD of the pipe, and assuming a production fluid with Cp=2,300 J/kg.K, density 140 kg/m3 and a k-value 0f 0.04 W/m.K, cooling from 50 C to 20 C in a 4 o C environment. Field life 20 years. Field operating at 95 o C. For shallow water to 200 m: System FBE Adhesive Inner solid Insulant Outer shield Total Compression (%) PPF spu ULTRA foam SG T cool (Hours) Jackson et. Al. BHR Conference, Antwerp, 2009 Page 13 of 14

14 For shallow water from m: System FBE Adhesive Inner solid Insulant Outer shield Total Compression (%) SG T cool (Hours) PPF ULTRA* * foam solid composite For shallow water from 500 m m: System FBE Adhesive Inner solid Insulant Outer shield Total Compression (%) SG T cool (Hours) PPF spp GsPU ULTRA* * foam solid composite For water depths >1000 m: System FBE Adhesive Inner solid Insulant Outer shield Total Compression (%) SG T cool (Hours) spp GSPU ULTRA FINAL COMMENTS Thermotite ULTRA is a new family of highly robust thermal insulation systems which has been developed and tested. The testing detailed in this paper adequately demonstrates that this system is suitable for use as a reliable thermal insulation system for subsea use, and is friendly toward pipe lay with the compatible field joint system. The improved thermal performance relative to market incumbents provides high thermal efficiency at reduced coating thickness. i Bredero Shaw Norway a.s. ii ShawCor LLC iii Norewgian Technical University iv Solheim, A., Aker Vetco A/S, Norway; Prichard, M., Vetco Gray Inc, USA; Newcombe, R., Vetco Gray Ltd, UK. Offshore Europe, 5 8 September v Direct Impedence Heating of Deepwater Flowlines, Hansen, A.B., Clasen, T.L. and Bass, R.M. OTC proceedings 1999 vi Auk pipeline, 12 km 8 inch line, buried to a depth of 1 m in 1986 vii DEH projects Statoil Åsgard, Statoil Kristin, Statoil Huldra, BP Skarv, Woodside Pluto Jackson et. Al. BHR Conference, Antwerp, 2009 Page 14 of 14

15 Thermotite ULTRA Superior Subsea Insulation FLOW ASSURANCE PRODUCT DATA SHEET Superior Insulation Properties 1. Fusion Bonded Epoxy 2. ULTRABond Adhesive 3. ULTRA Solid 4. ULTRA Foam 5. ULTRAShield Product Description Thermotite ULTRA is an innovative subsea insulation system with unlimited water depth capability, comprising a specially engineered blend of polymeric materials having unique mechanical and thermal properties. The superior performance of Thermotite ULTRA assures complete system integrity during service, and reduced energy loss in steady state and transient conditions. Lower thermal conductivity of both solid and foamed systems results in lower achievable U values Reduced thermal diffusivity extends cool-down time Compatibility with direct electrical heating systems (DEH) extends system utilization Unmatched Mechanical Performance Superior low temperature ductility enables lower temperature reeling and increased flexibility in installation schedule. Incompressibility of solid system allows unlimited water depth installation Higher insulation density coupled with reduced thickness improves seabed stability of flowlines and assists in optimizing hydrodynamic response of risers Thinner Insulation Lower thermal conductivity translates to reduced insulation thickness and potential savings in transportation and installation costs Thinner insulation and reduced pipe profile results in lower lay strains and improved hydrodynamic response Features & Benefits Applications No Glass Microspheres Zero risk of compromised thermal performance due to glass breakage or degradation during service Superior insulation performance without glass enables unlimited depth installation Proven Field Joint Technology Compatible injection-moulded field joint material guarantees insulation integrity and system performance Oil & Gas Pipelines Subsea Pipelines Small Diameter Pipelines Lower field-joint application temperature facilitates cooling and reduces moulding cycle time Application Using Conventional Equipment Streamlined delivery schedules, product standardisation and quality assurance practices due to simplified processing operations Universally and readily available project management and logistics support from multiple existing plant locations brederoshaw.com the GLOBAL LEADER in pipe coating solutions.

16 Thermotite ULTRA Superior Subsea Insulation Typical Plant Capabilities and Product Properties Capability/Property Thermotite ULTRA Diameter Range Maximum Water Depth... Unlimited as solid Density kg/m 3 Heat Capacity (Cp) J/kg K Thermal Conductivity (k) W/m K Axial Shear Strength... >10 Mpa Simulated Service... (tested up to) 280 bar at 95 C Outer Fiber Strain (Reel Lay)...2.6% strain at -10 C Values shown are typical and may vary from plant to plant. Consult Bredero Shaw for special requirements. Note: As density and composition are design variables with Thermotite ULTRA the above figures are given as general guidelines. Where there is a range specified, the interval is related also to the density range for the particular component. In addition, it should be noted that Thermotite ULTRA has passed tests for Resonant Fatigue, Trawl Board Impact, Stinger Roller and Tensioner Clamp. Product Application Process Thermotite ULTRA _rev021 Preheat Product Inspection Preheat Electrical Inspection Blast Clean Quench Grind Surface Defects 3-Layer Topcoat Extruded* Solid or Foam ULTRA Extruded Adhesive Quench Surface Inspection FBE Application Product Inspection Induction Heat HEAD OFFICE Bredero Shaw 3838 N. Sam Houston Pkwy E. Suite 300 Houston, Texas , USA Phone: solutions@brederoshaw.com NORTH AMERICA Bredero Shaw Two Executive Place, 200, 1824 Crowchild Trail, N.W. Calgary, Alberta T2M 3Y7, Canada Phone: northamerica@brederoshaw.com Regional Offices Plants Stockpile North America Latin America EMAR Asia Pacific Pearland, Texas Veracruz, Mexico Leith, Scotland Orkanger, Norway About Bredero Shaw Product Inspection Quench Extruded ULTRA Shield Kuantan, Malaysia Kabil, Batam Island, Malaysia Bredero Shaw is the global leader in pipe coating solutions. With more than 80 years of experience, the largest team of dedicated pipe coating professionals, the most extensive network of strategically located plants worldwide and with proven innovative coating technologies, the company has protected more pipelines in virtually every environment and operating condition than anyone in the industry. Bredero Shaw offers technologically advanced solutions for anti-corrosion coatings, protective and weight coatings, thermal flow assurance coatings, internal coatings, custom coatings and field joints for both onshore and offshore applications. This broad range of products and services provides Bredero Shaw with the unique capability to service the full spectrum of pipeline protection and flow assurance requirements. Consult your Bredero Shaw representative for your unique project requirements. Preheat * Insulation and outer shield layers may also be extruded by the crosshead method. LATIN AMERICA Bredero Shaw 3838 N. Sam Houston Pkwy E. Suite 300 Houston, Texas , USA Phone: latinamerica@brederoshaw.com EUROPE, MIDDLE EAST, AFRICA & RUSSIA Bredero Shaw Lakeside House 1 Furzeground Way Stockley Park, Uxbridge UB11 1BD Phone: +44 (0) EMAR@brederoshaw.com ASIA PACIFIC Bredero Shaw 101 Thomson Road #17-01/02 United Square Singapore Phone: asiapacific@brederoshaw.com The information contained herein is indicative of the types of coatings provided by Bredero Shaw, and is not intended to be a guarantee that a particular coating will be suitable for a given application. Since many unique environmental, operating, and design conditions must be considered, the user shall determine the suitability of the coating for the intended use and assume all the risks and liabilities in connection therewith. Bredero Shaw s liability is stated in our standard conditions of sale. brederoshaw.com the GLOBAL LEADER in pipe coating solutions.

17